package com.cloud.nio;


import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Arrays;

/**
 * Scattering 将数据写入到buffer时，可以采用buffer数组，依次写入【分散】
 * Gathering 从buffer读取数据时，可以采用buffer数组，依次读取
 */
public class ScatteringAndGathering {

    public static void main(String[] args) throws Exception {
        // ServerSocketChannel 和 SocketChannel 网络
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        InetSocketAddress inetSocketAddress = new InetSocketAddress(7000);

        // 绑定端口到socket，并启动
        serverSocketChannel.socket().bind(inetSocketAddress);

        // 创建buffer数组
        ByteBuffer[] byteBuffers = new ByteBuffer[2];
        byteBuffers[0] = ByteBuffer.allocate(5);
        byteBuffers[1] = ByteBuffer.allocate(3);

        // 等待客户端连接(telnet)
        SocketChannel socketChannel = serverSocketChannel.accept();
        // 假定从客户端接收8个字节
        int messageLength = 8;

        // 循环读取
        while (true) {
            int byteRead = 0;
            while (byteRead < messageLength) {
                long read = socketChannel.read(byteBuffers);
                byteRead += read;
                System.out.println("byteRead = " + byteRead);
                // 使用流打印，看看当前的这个buffer的 position 和 limit
                Arrays.asList(byteBuffers).stream().map(byteBuffer -> "position=" +
                        byteBuffer.position() + ", limit="+byteBuffer.limit()).forEach(System.out::println);

                // 将所有的buffer进行flip
                Arrays.asList(byteBuffers).forEach(byteBuffer -> byteBuffer.flip());

                // 将数据读出显示到客户端
                long byteWrite = 0;

                while (byteWrite < messageLength) {
                    long write = socketChannel.write(byteBuffers);
                    byteWrite += write;

                    // 将所有buffer 进行clear 复位
                    Arrays.asList(byteBuffers).forEach(byteBuffer -> byteBuffer.clear());

                    System.out.println("byteRead = " + byteRead);
                    System.out.println("byteWrite = " + byteWrite);
                    System.out.println("messageLength = " + messageLength);
                }
            }
        }

    }
}
